Did Mercedes get their rear axle rotations all wrong?

[@morganjoe1]

This is exactly why we changed the rear axle gear ratios on our 1971 W 108 M130. Great work, Pierre!!

[@azmike3572]

Great German accent!

[@christophermarshall5765]

One of my friends had a 450SEL. The diff started getting noisy, so we replaced it with the 2.65:1 diff out of the 450SEL-6.9. It has good fuel economy, and higher top speed.

[@cardiffchris]

I had a 1972 Mercedes Benz 250, It needed longer gearing. The first gear was so short and would shift itself into 2nd after about 10 feet. Always felt like it needed an overdrive.

[@RuperScooper]

That German accent was gold cracked me up 👍🇩🇪

[@ricochetx]

Came here to say this! 😂 Pierre’s been holding out on us.

[@om602fan]

You absolutely have got the point. It is a bit different on the roads in Europe. Trucks are going 56 mph so you as long as you not letting them to overtake you you can maintain 60 mph on the motorways and would not bother anyone.

[@myronsogaugetrains6825]

Hope your doing well and in good health!!! With all the hurricanes !

[@ExAnimoPortugal]

These older Benzes were not made for the Autobahn If you drive in Germany, most times you are on the Landstrasse, where you're doing 45-50, maybe 60 most of the time.

[@ronalddean3630]

Huh? I thought they all were...

[@reneej.deeter9814]

I changed my 77 240D mt4 speed to a 3.07. Now a reasonable rpm at 70mph. I did find some issues with lack of power on /in hills. Also very steep grades in 1st are tough. Need 5speed and different tranny ratios. My 190e 2.6 AT never uses 1st and could use taller rear gearing. Thinking of making it manual 5speed.

[@fredc106]

I always felt my 1987 560SL could benefit from an over-drive. In southern cal there were miles of fast freeways in the 1970s and on. I also had a 327 Stingray geared a little higher (about 2000 rpm at 60-65 mph, IIRC), also could have used an over drive. Biggest trouble was the engine basically wore out at about 100K, and the Quadrajet was a big pain. OTOH, the 560 still strong at 180K and the biggest problems are the usual replacements you discuss in your posts. My biggest problem is just getting in and out of the car (too many birthdays). At some point I am going to have to let the 560 go. That will be a sad day.

[@jessiedazzle]

I would concur 100%. What we really need is a good, reliable, simple, 7 or 8 speed transmission that can handle the torque of the various vehicles we own. 7-8 ratios implies a recently-produced transmission. It should not be impossible if one is OK with a manual transmission. Any "modern" automatic is going to be electronically-infested which would make successful integration very challenging and, if successful, the result would be a departure from the bulletproof simplicity of our cars.

[@myronsogaugetrains6825]

Is a 1958 220s easy to work on ?

[@michaelmcfeely6588]

rotations or ratios?

[@lucasp3894]

I swear the guy who uploads pierre's videos on youtube doesn't even try lol

[@cameronwebb5992]

@@lucasp3894absolutely does NOT try 🤭🤭

[@weedie82]

Those daggum rear axle rotations will mess w/ u everytime!😂!

[@baltobenz9508]

Years ago you wrote an article in the Star about w113 ownership where you briefly addressed the gearing issue by pointing out that these cars often came in having aftermarket overdrive units installed in them. I wondered who made these units and where I could get one for my w112 coupe. My temporary “solution” is to run 225 R14 tires, which gives me an extra 5-8 MPH for the same RPM at highway speeds.

[@averyalexander2303]

Depending on how you drive and many other factors, I wouldn't expect an aftermarket overdrive unit to gain you much MPG due to the extra weight, rotational mass, and frictional losses it adds. At the same speed and RPM, you'd definitely get better MPG with a taller final drive than an overdrive unit. Remember that it takes a fixed amount of power to travel at a given speed, and that's determined by aerodynamics, rolling resistance, etc. If it takes, for example, 30HP to go a steady 70 MPH, you can't change that with gearing. The benefit is the engine tends to be more efficient at a higher load (torque) and lower RPM, but if you add weight and drag with an additional overdrive unit, you force the engine to generate MORE power to go the same speed, which cuts into your savings from running the engine at a more efficient load/RPM.

[@liljawn826]

My W124 300D 2.5 was an infinitely more highway ready car than my W123 300D is. That 3 or 400RPM under 3000 made all the world of difference.

[@ksben0016]

I have a 1989 300E which had an upper hose manifold crack and fail while in a drive through. Car was towed to my house where I replaced the radiator with one from autozone. Afterwards, I started having issues where in reverse my car vibrates badly and sometimes doesn’t move at all. Forward gears work fine. Car was dragged on to a flat bed from the rear when towed. Any idea on the cause and or fix?

[@5aldl]

Now I have replaced a differential for my 450slc, from 3.47 to 3.07, the donor car had a stiffer drive shaft, what will that affect? Now what I got after replacing the differential and keeping the thinner driveshaft is I got 500rpms lower, but my speedometer starts reading less than actual speed after 75km/h gradually until the difference reaches 15km/h at 120km/h. So when I'm driving at 120, cluster is reading around 105, if I used the stiffer driveshaft, what will it affect? RPMs and speedometer reading? And should I replace the cluster from the same car as well? Because the gearings are different ?

[@AlienLivesMatter]

I feel like the 3.6 differential in my 300se w126 is perfection

[@sirjosephwhitworth9415]

I have a W108 280S with the later 3.69 axle, it's fine here in England on most roads and the motorway, but, 65 to 70 mph is where it is comfortable. That suits me I just enjoy cruising around in it, for speed I have a new 5er Touring for doing the 200km + on the Autobahn in Germany. Horses for courses. Good video.

[@mickeymichaels1298]

Modern Mercedes had much taller axle ratios for two reasons. One is that Mercedes became much more concerned with fuel economy and emissions in more modern times. The other one is the switch to torque converters as compared to the fluid couplings with no torque multiplication of the old Mercedes transmissions, therefore they needed the steep rear end ratios. Our 72 250 had a 3.69:1 differential and still couldn't get out of its own way. It definitely did some revs on the highway but we were used to it, so it seemed normal to us. 😁

[@ronalddean3630]

This is what I mean, tall ratio vs short ration, what does that mean? I get that one may shift sooner than the other...but beyond that.

[@mickeymichaels1298]

@@ronalddean3630 tall or high gearing means that for a fixed speed in top gear, the engine is going slower (at lower RPM). It equates to a smaller axle ratio number, such as 3.08. Short or low gearing uses an axle ratio with a bigger number, such as 4.08. Tall gearing results in a lower engine speed (lower RPM) at the same speed in top gear. Yes, you read that right. Tall gearing means a low number and short gearing is achieved with a high number when talking about axle ratios. In this hypothetical example, imagine two otherwise identical cars except for axle ratios. In top gear the one with the short axle ratio of 4.08 is driving at whatever speed corresponds to 4000 RPM. Driving at the same speed in top gear in the car with tall gearing (axle ratio of 3.08), the engine is only doing about 3000 RPM.

[@BalyAlbert]

I have a W124 from 91 with an M103 engine but the 2.6 version. I swapped the rear differential from a 3.27 ratio to a 3.07 ratio because of the high rpms while cruising on the highway. Now, with 140km/h (that is about 90 miles) I get around 4000 rpms. Could that rpm number damage the engine in time if I travel longer distances on the highway?

[@averyalexander2303]

No. Many cars, even much more modern ones, are geared shorter than that and still last hundreds of thousands of miles no problem. Some of them even became legendary for their ability to last almost forever. Old Hondas and MB diesels come to mind. The load (torque) on the engine is actually lower with shorter gearing. Think of how much easier a bike is to pedal in a lower gear than a higher gear. Within the normal operating range, it's debatable whether a higher load or a higher RPM causes more wear when the engine is generating the same HP either way. If you are worried or don't like the sound, you can always slow down a little if you prefer. If nothing else, you'll save some fuel :)

[@BalyAlbert]

@@averyalexander2303 thanks for your answer. I don't mind the sound because it is not that loud. The M103 is an inline 6 cylinder engine, pretty refined and not loud and it has a pretty good soundproofing as well. The thing is, modern cars have more gears not just 4 like my car plus the differential is tuned differently.

[@gusibrahim6961]

I think they got it wrong because i slotted 280 engine in a 450 SLC and the result was astounding

[@jaymoney1252]

My 91 300SE does 70mph at about 3500rpm, 80mph at 4000rpm, I’ve only done 80mph a handful of times since I’m worried of putting stress on the engine

[@jaye909]

Even my 2008 VW Jetta 5MT is spinning 3600 rpm at 80mph! They should have put a taller 5th gear or simply made it a 6 speed.

[@ronalddean3630]

I enjoyed the video, useful as always, but I have to say, this went right over me head 😵‍💫If there is someone who would like to break it down for me...feel free. The German accent was great. LOL

[@classicjalopy]

Its interesting that USA got special ratios that the rest of the world didn't. My 250SE has a 3.92 rear end but USA got 4.08. Not a huge difference but still a difference.

[@averyalexander2303]

A lot of European market cars still get taller ratios than the same model sold in the US. Makes sense because of their higher fuel costs and it makes sense in Germany for the Autobahn, but a lot of Americans also regularly drive long distances at high speeds. I'd like to eventually get the European 4.1 final drive for my 6 speed Honda. Even after installing the tallest available 6th gear from another model, the US market 4.4 final drive is still too short for my preferences.

[@Altanox]

Gonna change my 3.46 for a 2.88 soon (300D NA)

[@sebjebofficial6230]

Having a 1984 300SD, it would be nice to have a 2.47 diff in it.

[@Penguinracer]

Modern traffic density & speed is not something for which many of these cars of the '50's, 60's & 70's were designed. The higher diff ratio makes sense for modern conditions.

[@ronalddean3630]

The 240D was Mercedes' most successful car in city driving, AKA Taxi Cabs...I am not following 🧐

[@W115-m5f]

What if your engine only has 65HP ? Is a 3.92 the best Option then ?

[@averyalexander2303]

There is no "best" gearing. It's entirely dependent on your preferences and how and where you use the car. Like everything else, gearing is a compromise, especially when you only have 3-4 gears and not much power. An axle ratio that would be great for long distances at high speeds on flat roads probably wouldn't work well for someone driving around in low speed city traffic in San Francisco or some other hilly place. And even then, you still have to decide what RPM you want to run at on the highway, what kind of performance and response you want, etc.

[@glotube1028]

The Man bun is cool! All soccer players have them. I have to laugh because your such a huge guy out there, kicking the ball around. You must be towering over everyone! I’ve always wondered why Mercedes made their cars with so high of rpm on the road. My little w115 220 really wines out at 70, and it’s loud. It’s much happier at 55. I love that little car! Rusty but trusty and has a good patina.

[@ronalddean3630]

@@glotube1028 hi, may you elaborate a little on your comments? This discussion is over my head...I am not really following and fully understanding it. Pierre and "Uncle Kent" from Mercedes Source have both said that when, for example, a 240D has proper settings on it, getting up to speed is not as much of an issue as some may think or experience. Do you mean the car won't hold its speed at 60-70? Thanks

[@glotube1028]

No it will hold 70, but the rpm’s are at 4,000 so it’s really at its max.

[@omzysgarage9323]

Horrible on the highway. It needs a 5th gear for sure. The sweet spot for economy with standard diff is around 60km/h. The w201 sounds like it's lifting off at 100km/h. Good info, thanks for the video.

[@averyalexander2303]

The way a lot of manual transmissions are geared is wrong IMO. Most of them would benefit from a taller top gear and many from a taller final drive too. I know manufacturers gear their cars so short because they want to make the driver feel like it's more powerful than it really is and because people complain about having to downshift to climb big hills or pass. However, forcing drivers like myself who have enough of a brain to realize they bought a manual transmission and need to shift it when required to cruise at 3-4K RPM and get lower MPG just so some lazy idiot doesn't have to downshift from top gear to accelerate up a 7% grade is absolutely ridiculous.

[@vintage76vipergreenBeetle]

Nothing wrong, with reducing rpm's on highway driving on a vintage MB.

[@jptech57]

Good points, Pierre. Overdrive would be a revelation for a lot of these cars. I have to downvote the man-bun, though.

[@tymwalt]

Pierre plays soccer?

[@chumpthetraitor7331]

Football

[@mariocaja3279]

Sprechen Sie Deutsch?

[@anthonynicholich9654]

What you are failing to recognize is while american cars had 2 and 3 speed transmissions German cars were all 4 speed and if they reved as high as you ssy how were the top speeds higher than any other cars? I'm talking 130 140 even a 150 MPH in a 450 and 500SEL? You are not entirely right.